When れる(reru) expresses ability, it only applies to godan verbs and the -ar- in the result is contracted, e.g., 読 (よ)む(yomu) → 読 (よ)ま(yoma) + れる(reru) → 読 (よ)める(yomeru). れる(reru) expressing ability does not apply to the irregular verb する(suru), whose potential form is another verb, できる(dekiru).